[1] Proanthocyanidins are under preliminary research for the potential to reduce the risk of urinary tract infections (UTIs) by consuming cranberries, grape seeds or red wine.
[2][3] Proanthocyanidins, including the lesser bioactive and bioavailable polymers (four or more catechins), represent a group of condensed flavan-3-ols, such as procyanidins, prodelphinidins and propelargonidins.
[11] The seed testas of field beans (Vicia faba) contain proanthocyanidins[12] that affect the digestibility in piglets[13] and could have an inhibitory activity on enzymes.
Gel permeation chromatography (GPC) analysis allows separation of monomers from larger proanthocyanidin molecules.
[6] They are dense in grape seeds and skin, and therefore in red wine and grape seed extract, cocoa, nuts and all Prunus fruits (most concentrated in the skin), and in the bark of Cinnamomum (cinnamon)[4] and Pinus pinaster (pine bark; formerly known as Pinus maritima), along with many other pine species.
OPCs also can be found in blueberries, cranberries (notably procyanidin A2),[26] aronia,[27] hawthorn, rosehip, and sea buckthorn.
[6] In nature, proanthocyanidins serve among other chemical and induced defense mechanisms against plant pathogens and predators, such as occurs in strawberries.
[32] These techniques are generally called depolymerisation and give information such as average degree of polymerisation or percentage of galloylation.
The reaction leads to the formation of free and derived monomers that can be further analyzed or used to enhance procyanidin absorption and bioavailability.
In general, reactions are made in methanol, especially thiolysis, as benzyl mercaptan has a low solubility in water.
[39] Clinical trials have produced mixed results when asking the question to confirm that PACs, particularly from cranberries, were an alternative to antibiotic prophylaxis for UTIs: 1) a 2014 scientific opinion by the European Food Safety Authority rejected physiological evidence that cranberry PACs have a role in inhibiting bacterial pathogens involved in UTIs;[2] 2) an updated 2023 Cochrane Collaboration review supported the use of cranberry products for the prevention of UTIs for certain groups.
[40] In 2019, the American Urological Association released guidelines stating that a moderate level of evidence supports the use of cranberry products containing PACs for possible prevention from recurrent UTIs.
[41] Proanthocyanidins are the principal polyphenols in red wine that are under research to assess risk of coronary heart disease and lower overall mortality.
[45] Proanthocyanidins found in the proprietary extract of maritime pine bark called Pycnogenol were not found (in 2012) to be effective as a treatment for any disease: Proanthocyanidins are present in fresh grapes, juice, red wine, and other darkly pigmented fruits such as cranberry, blackcurrant, elderberry, and aronia.